Document ability to specify which host-only network.
Document ability to specify which host-only network.

Although it has been possible to specify a specific VirtualBox host-only network
to attach a machine's NIC to, this was never mentioned by the documentation in
the VirtualBox provider's networking section. I had to spelunk through the issue
tracker to find an example of this.

This patch adds a code example along with a short description of the ability in
human language prose, and a link to the relevant section in the VirtualBox User
Manual about "Host-Only Networking."
chrisroberts/vagrant,chrisroberts/vagrant,chrisroberts/vagrant,marxarelli/vagrant,marxarelli/vagrant,mitchellh/vagrant,mitchellh/vagrant,marxarelli/vagrant,mitchellh/vagrant,chrisroberts/vagrant,sni/vagrant,sni/vagrant,sni/vagrant,sni/vagrant,marxarelli/vagrant,mitchellh/vagrant